STM32F3 correct analogin_read

[jeromecoutant]

Description

There was an issue with ADC and STM32F3 targets when several measurements were requested by application.

Tests

Manual tests with internal channels OK

Ci tests OK:

target	platform_name	test suite	result	elapsed_time (sec)	copy_method
NUCLEO_F303ZE-ARM	NUCLEO_F303ZE	tests-api-analogin	OK	15.26	default
NUCLEO_F303ZE-ARM	NUCLEO_F303ZE	tests-api-analogout	OK	13.9	default
NUCLEO_F303ZE-ARM	NUCLEO_F303ZE	tests-assumptions-analogin	OK	18.06	default
NUCLEO_F303ZE-ARM	NUCLEO_F303ZE	tests-assumptions-analogout	OK	13.46	default

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Breaking change

[cmonr]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3137
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8131/

Triggering tests

/morph test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2744
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8131/

[mbed-ci]

Test : FAILURE

Build number : 2941
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8131/2941

[0xc0170]

/morph test

[mbed-ci]

Test : SUCCESS

Build number : 2953
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8131/2953